The invention relates to an audio system, and in particular to an audio system and method that includes an FM receiver that provides an audio signal and a reception signal to a multichannel sound production system. The multichannel sound production system provides a plurality of speaker output signals encoded in response to the reception signal.
FM stereo receivers are often equipped with a control unit that controls the stereo and mono components within its audio output signal in response to the reception quality. The term used in this regard is “channel separation” which is especially suitable for use in FM stereo receivers in vehicles, since the reception quality for stereo reception is often not sufficient due to the conditions under which the vehicle is driven at any given time. For this reason, the stereo component in the reproduced signal is reduced when reception conditions worsen, while the mono component is simultaneously increased. This shift from stereo to mono during poor reception conditions may reach the point of complete mono reproduction.
A multichannel sound reproduction system with a plurality of speakers may be connected to this type of FM stereo receiver. The reproduction system generates a plurality of reproduction signals for a plurality of speakers to improve the spatial acoustic pattern from the audio output signal supplied by the FM stereo receiver. However, when the stereo component in the audio output signal from the FM stereo receiver decreases, while the mono component increases, the perceived audio quality of the spatial acoustic pattern of the multichannel reproduction decreases—with the ultimate result often being a complete breakdown of the spatial acoustic pattern. As a result, strong fluctuations in reception quality during mobile operation result in an unacceptable drift in the acoustic pattern.
Therefore, there is a need to improve the acoustic pattern for a multichannel reproduction system connected to an FM stereo receiver, in response to a degrading stereo signal, and to reduce/prevent the drift in the acoustic pattern under conditions of fluctuating reception quality.